Compact, low-power-consumption light sources on which LED elements are mounted are frequently used in illumination for improving the visibility of displays, active displays for home electronics and industrial products, and other such applications.
In order to supply electricity to the LED element of such a light source, wiring is imprinted on a ceramic substrate using silver paste and the ceramic substrate is sintered, whereby an electricity-supplying circuit is formed.
However, a problem is presented in that light reflectivity changes with the color and width of the silver wiring layer forming the electricity-supplying circuit. When a surface mount chip LED or the like is installed on the ceramic substrate, the chip LED needs a reflector.
Furthermore, an advanced installation technique is necessary to produce a light source having exceptional uniformity and positional accuracy in a light-emitting state.
In the past, there have been known light-emitting devices having LED elements built into an airtight container in which an LED is accommodated on a substrate comprising an inorganic material, a phosphor layer is applied to an inner surface of the airtight container, and a vacuum atmosphere or an inert gas atmosphere is present inside the airtight container (Patent Document 1).
However, when a chip LED is mounted on a ceramic substrate, it is difficult to adjust the flatness of the ceramic substrate, the angle of the attached reflector, and the flatness of the surface mount. Therefore, it is difficult to obtain a stable light-emitting surface because the axis at which the light is emitted by the chip LED varies.
When an LED display is configured using a single LED element as a single pixel, conventional LED elements must have a plastic or other enclosure formed thereon as with molded-plastic LED elements, and the external dimensions thereof make it harder to increase the resolution of the LED light-emission spacing.